Glyphicon tweaks

BS3 commits: a4497c8a831fc96e5e2fefb7cf1570d81d957296
Fix Issue 15076.

BS3 commits: 2006a435d98b51a8d8430abe14ac3611113c2dff
Wash-up of some stray dropdown examples

BS3 commits: 56f41561260651fc67fcbe7ce65f7aa7fc79788f
move single-toggle button plugin callout before example for consistency

BS3 commits: 3b2d1570fa85c0faac0e7da65b415e59996f4300
move carousel accessibility callout next to rest of callouts

BS3 commits: 5ba52001952b6a0744fc17252c0a07b97a836583
move popover examples heading to directly before the actual examples

BS3 commits: e2e9613f8359189cc11a5c6c577f013b677dd59e
move scrollspy callouts so they're all adjacent to each other

BS3 commits: 69d42cef141624491705b0dafcf30b2f13f319a2
add missing dots to .sr-only class mentions, for consistency w/ rest of docs

BS3 commits: 125945eb9058ad8db1f3843259ee9aa73e9bec5f
grunt

BS3 commits: ff386147ce341a15f02b31f638500487246e34da
Glyphicon tweaks

BS3 commits: a4497c8a831fc96e5e2fefb7cf1570d81d957296
Fixed a typo in Sign-in page example

BS3 commits: 542c1040aae2da79432168e46d8e8efcd1363f48
navbar callouts cleanup

BS3 commits: b87370c28f6f8cd0d2de6cc541dcba22788e4001
masthead and toolbar callouts cleanup
add Overflowing content callout
grunt

BS3 commits: 143c4a2f8fc91513dc656e7bf3f234d21a45f849